This study's long term objective is to provide a better understanding of determinants of health service use among youth with co-morbidities (those with both a substance abuse and psychiatric disorder). This study also compares patterns of service use for youth with substance abuse and/or psychiatric disorders in rural vs urban areas. This study has 2 specific aims: 1) To use state-of-the-art multilevel statistical models to investigate the relative importance of patient and provider characteristics as determinants of inpatient length of stay (LOS) and quality of care (measured as receipt of followup services and probability of readmission); 2) To use sophisticated Geographic / Information System technology to incorporate information on community characteristics that affect access to health services in the multilevel analyses. The hypotheses focus on 3 questions: a) How does the nature of a youths co-morbidity affect his or her service use pattern?; b) How much influence do providers have on services received by children and adolescents with substance abuse and/or mental health problems?; and c) How do geographic attributes such as distance to provider affect receipt of care among youth with substance abuse and/ or mental health conditions? These analyses will draw on Medicaid claims data from the Tennessee Impact Study and The Substance Abuse Prevention and Treat Block Grant. The Area Resource File will provide information on community level factors. The population for this study is youth aged 12-17 in 1997 and enrolled in the Tennessee Medicaid program. Our data provides information all inpatient stays in residential facilities, detox facilities and inpatient hospitalizations where the youth's primary diagnosis was substance abuse or mental health related. LOS will be estimated using a multilevel hierarchical cross-classified model, readmissions and follow-up will be modeled using a multistate competing risk model. Models will incorporate distance to providers and other measures of access to health services through the use of GIS. [unreadable] [unreadable] [unreadable]